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# Homebrew

* <https://github.com/Homebrew>
* <https://github.com/Homebrew/brew>
* <https://github.com/Homebrew/homebrew-core>
* <https://github.com/Homebrew/homebrew-cask>

[**Terms**](https://docs.brew.sh/Formula-Cookbook#homebrew-terminology)**:**

* Formula - package definition.
* Keg - installation prefix of a formula.
* Cellar - where all kegs are located.
* Tap - git repo of formulae and/or commands.
* Bottle - pre-built keg.
* Cask - extension of Homebrew to install native MacOS apps.

**General notes:**

* I like how formulae come with tests.
* Formula dev guide is pretty great.
* Ruby seems like a great choice for DLSs like this.
* Overall code structure seems moderately simple, e.g. there are not too many layers of redirection for the most part.
* Implementation details are often rather convoluted, with not too many comments.
* A lot of long methods.

**Tracing:**

* Entry point shell script: <https://github.com/Homebrew/brew/blob/master/bin/brew>
* Then <https://github.com/Homebrew/brew/blob/master/Library/Homebrew/brew.sh>
  * Setting env variables for OS, cache location, etc.
  * Checks that it's not sudo, not installing on temp, etc.
  * Check dependencies: curl, git, ...
  * Then route to one of <https://github.com/Homebrew/brew/tree/master/Library/Homebrew/cmd>
    * Some are .sh, some are .rb
    * I expected a single ruby entry point, but there's none!
* Install path:
  * <https://github.com/Homebrew/brew/blob/master/Library/Homebrew/cmd/install.rb>
    * Test: <https://github.com/Homebrew/brew/blob/master/Library/Homebrew/test/cmd/install_spec.rb> Seems rather... superficial. But I kind of like their test DSL.
  * Command parser: <https://github.com/Homebrew/brew/blob/master/Library/Homebrew/cli/parser.rb>
  * Check if to install: <https://github.com/Homebrew/brew/blob/aa14e48f4e73d2f4c7d178d7b8a2f528b74995d7/Library/Homebrew/install.rb#L95>
  * Install: <https://github.com/Homebrew/brew/blob/aa14e48f4e73d2f4c7d178d7b8a2f528b74995d7/Library/Homebrew/install.rb#L232>
    * Accepts formula and a ton of params.
    * I would probably extract the params into some class.
  * Then it creates [FormulaInstaller](https://github.com/Homebrew/brew/blob/aa14e48f4e73d2f4c7d178d7b8a2f528b74995d7/Library/Homebrew/formula_installer.rb#L29) and calls its methods one by one: prelude, fetch, install, finish.
  * FormulaInstaller seems... rather convoluted.

**Interesting:**

* Did you mean? <https://github.com/Homebrew/brew/pull/11565/files>
  * Not too interesting. It just delegates.
* Locking. <https://github.com/Homebrew/brew/blob/master/Library/Homebrew/lock_file.rb>
* Github access <https://github.com/Homebrew/brew/blob/aa14e48f4e73d2f4c7d178d7b8a2f528b74995d7/Library/Homebrew/utils/github.rb> With pagination and what not. Spec: <https://github.com/Homebrew/brew/blob/master/Library/Homebrew/test/utils/github_spec.rb>
* Search: <https://github.com/Homebrew/brew/blob/master/Library/Homebrew/search.rb>
* Download strategy switch: <https://github.com/Homebrew/brew/blob/09f7bc27a99469cf947431df4754737dfbadb31d/Library/Homebrew/download_strategy.rb#L1323-L1356>
* Unpack strategy. <https://github.com/Homebrew/brew/blob/master/Library/Homebrew/unpack_strategy.rb> <https://github.com/Homebrew/brew/tree/master/Library/Homebrew/unpack_strategy>
* Cache store: <https://github.com/Homebrew/brew/blob/master/Library/Homebrew/cache_store.rb>
* Curl & workarounds: <https://github.com/Homebrew/brew/blob/04532cb6216b69a5b067aa7a4e22cff0944b257d/Library/Homebrew/utils/curl.rb#L64>